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Formal deformation of curves with group scheme action

Stefan Wewers (2005)

Annales de l’institut Fourier

We study equivariant deformations of singular curves with an action of a finite flat group scheme, using a simplified version of Illusie's equivariant cotangent complex. We apply these methods in a special case which is relevant for the study of the stable reduction of three point covers.

Fragmented deformations of primitive multiple curves

Jean-Marc Drézet (2013)

Open Mathematics

A primitive multiple curve is a Cohen-Macaulay irreducible projective curve Y that can be locally embedded in a smooth surface, and such that Y red is smooth. We study the deformations of Y to curves with smooth irreducible components, when the number of components is maximal (it is then the multiplicity n of Y). We are particularly interested in deformations to n disjoint smooth irreducible components, which are called fragmented deformations. We describe them completely. We give also a characterization...

Frobenius nonclassicality with respect to linear systems of curves of arbitrary degree

Nazar Arakelian, Herivelto Borges (2015)

Acta Arithmetica

For each integer s ≥ 1, we present a family of curves that are q -Frobenius nonclassical with respect to the linear system of plane curves of degree s. In the case s=2, we give necessary and sufficient conditions for such curves to be q -Frobenius nonclassical with respect to the linear system of conics. In the q -Frobenius nonclassical cases, we determine the exact number of q -rational points. In the remaining cases, an upper bound for the number of q -rational points will follow from Stöhr-Voloch...

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